Eliminating vibration and shocks to smooth the ride for a person sitting upon a vehicle traveling over rough ground has been a serious problem since the development of the first vehicle. Solutions have typically involved isolating the wheels of the vehicle from the vehicle frame by means of springs and shock absorbers, as well as spring mounting the vehicle seat on the vehicle frame. In automobiles and tractors, for example, seats have been mounted using both coil springs, leaf springs, and combinations thereof.
Referring particularly to the bicycle art, wherein the present invention has relevant application, the seat support almost universally takes the form of a rigid seat post inserted into a hollow vertical tube of a rigid bicycle frame. A seat, which may include a form of resilient spring cushioning, is mounted to the top of the seat post.
A number of prior art bicycles have incorporated shock absorbing systems within the frames to absorb vibration and shocks. For example, U.S. Pat. No. 5,356,165 to Kulhawic et al. discloses a bicycle that has a two-piece frame, with the two pieces of the frame separated by a shock absorber. Other prior art bicycle designs have incorporated shock absorbers in the forks or in other portions of the bicycle frame.
A few designs of prior art bicycles incorporate seat suspension systems that include shock absorbers beneath seat supporting beams. An example of one of these bicycles is disclosed in U.S. Pat. No. 496,093 to Okey. The Okey patent discloses a seat suspension beam pivotally secured near the head tube of a bicycle and suspended with a helical coil spring shock absorber.
U.S. Pat. No. 4,934,724 to Allsop et al. teaches a unique way of providing support for a bicycle seat. The Allsop patent discloses an elongate seat support formed by an elastomeric member sandwiched between two composite beams. One end of the elongate support is attached to the bicycle frame. The seat is supported at the cantilevered opposite end of the elongate support.
The elongate seat support disclosed in the Allsop patent is particularly advantageous in that the composite beams and the elastomeric material allow for two different types of shock absorbing action. Suspension action in the bicycle introduces shear stress in the elastomeric member, which provides damping of low amplitude modulation of the frame. Shock absorption is provided by the beams as they flex relative to one another and relative to the bicycle frame. Thus, the elastomeric material provides damping of smaller, low amplitude vibrations in the bicycle, while the beams provide shock absorption from low and high amplitude vibrations.
The elongate seat support disclosed in the Allsop patent offers a type of suspension not available in other prior art designs. Because the elongate seat support utilizes suspension of the seat and rider, and not separate frame pieces, substantially all of the rider's pedaling efforts are transferred to the wheel. For example, the bottom bracket of the bicycle, to which the crank assembly is mounted, is rigidly connected to the axle for the rear wheel. The rear wheel does not include a suspension system, so none of the rider's pedaling efforts are wasted on suspension action. In addition, because there are no shocks or suspension elements in the front forks, the front wheel is rigidly connected to the frame. This rigid connection permits optimal steering efficiency for the bicycle.
Although the elongate seat support in the Allsop patent provides optimal pedaling and steering efficiency, there exists a need for a bicycle suspension that provides the advantages taught by the Allsop patent but is less expensive to manufacture and is lighter in weight.